Authorities say a 13-year-old boy is dead and his father and younger brother critically injured after the pickup truck they were riding in struck a big rig on Phoenix's Interstate 17.
Arizona Department of Public Safety officials say the man and his two sons were driving Monday afternoon from Rock Springs to their Gilbert home when their vehicle drifted into the shoulder near Jomax Road.
The pickup struck the semi, which was pulled over along the highway because of a flat tire.
After the pickup hit the big rig, authorities say a tow truck driving south on the I-17 hit the truck.
"As you can see, the force of the impact sheared off the front right side of the pickup truck. It careened off the semi. A tow truck that was behind this tried to take evasive action to avoid hitting the pickup truck, but could not stop in time and struck the pickup truck as well," said DPS spokesperson Bart Graves.
The victim's 50-year-old father and his 11-year-old brother, a backseat passenger, were hospitalized in critical condition.
The driver of the tow truck sustained non-life threatening injuries, and the driver of the semi was not hurt.
Officials say all southbound lanes of the I-17 were closed for hours after the 2:45 p.m. accident.
Traffic was taken off at State Route 303 as DPS worked to clear the wreckage and determine the cause.
DPS has not ruled out fatigue as a factor in the crash. The investigation is ongoing.
The Associated Press contributed to this report.